Bayonetta 1 & 2. The second Bayonetta needs to be played by more people. Bayonetta 2 also suffered from framerate dips when things got a bit crazy, something that can easily be fixed on the Switch.

The Legend of Zelda: The Wind Waker HD and The Legend of Zelda: Twilight Princess HD also need a port. Both titles suffered framerate dips on the Wii U - in places that had no frame issues on the original versions at that. The Wind Waker HD was the most noticeable in my opinion. When you were on the boat taking out other boats and cannons in the reefs, things would stutter a bit.
Hopefully they can be released in a collection together, with the possibility of Skyward Sword HD too (I know that this currently does not exist, however, Skyward Sword HD needs to happen).

Xenoblade Chronicles X would make for a good port too. They can improve/remove the pop in that happens in the city. Increase the resolution, and perhaps create hit detection with the vehicles in the city too. I also think that a HD port of Xenoblade Chronicles would be excellent.

Donkey Kong Country Returns and Donkey Kong Country Tropical Freeze need to appear is some capacity. Donkey Kong Country Returns still looks excellent (especially for a Wii title). Include the 3DS content and make the game 1080p. Donkey Kong Country Tropical Freeze would also benefit from being rendered in 1080p. These two games should be bundled together.

Pikmin 3 would look amazing with updated textures and being rendered in 1080p.

I considered listing Super Mario Maker, however, I think a pseudo sequel would be better. Include all the tools that were in the original, plus more. Incorporate slopes, water for non-water levels, more enemies etc.

I feel like if they were to release a Super Smash Bros. for Wii U/3DS port, they should have done so by now. This is the type of port that would benefit from an early release rather than later. At this point a new title is far more necessary.

A definitive edition of Captain Toad would be cool. Have the game rendered at 1080p with extra stages and perhaps some sort of online ranking mode with multiplayer perhaps? I think that a multiplayer mode for Captain Toad could potentially be a lot of fun. Have a co-op mode where you have to navigate the area together and find treasure and/or a mode in which you hurl turnips at each other. Something that sounds so ridiculous would be a lot of fun if done correctly.

I think they might as well and go ahead and port basically every good game from Wii U. Not all have to be retail releases. Things like Wonderful 101 can be an eShop only thing and priced at a lower price point.

Wii Sports (although I'd prefer Resort which was on the original Wii).

Mario Maker would be cool but I bet we'll get Mario Maker 2 with more level backgrounds and more options (because why not? They can just use the foundation of the first game and add to it). Same goes for Smash, at this point I think it's too late for a port and we'll get a new one in 2019.